• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.6
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• pp.285-291
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• 2002

In this paper, the LPA(Linear Power Amplifier) using new analog feedforward linearizer for IMT-2000 frequency band(2110MHz∼2170MHz) is proposed and fabricated. The designed analog feedforward linearizer system possessing the characteristics of stable operation for input power variation is simple structure and small size. When two-tones in IMT-2000 frequency band are applied to an amplifier, this LPA have the average output power is about 30W and the IMD value is below about 60dBc without correcting the circuit. In camparision with an amplifier without feedforward system at the same output power, the supposed analog feedforward linear amplifier posseses improved the IMD characteristics of over 23dB.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9C
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• pp.1306-1315
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• 2004

UWB, which is now in a process of being standardized in WPAN communication, has some problems such as difficulty of implementation and interference with existing systems. To overcome these problems we will explain the MIMO structure to alleviate difficulties of implementation. In this paper we propose the UWB transceiver structure using multiband scheme to mitigate narrow band interference from PCS Of WLAN which is widely used these days and analyze the effect of noise and narrow band interference by simulation based on numerical analysis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.2A
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• pp.139-148
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• 2011

This paper presents the minimum-cost network selection scheme which determines the transmission instance in the multi-band maritime communication system, so that the shipment-related real-time information can be transmitted within the maximum allowed period. The transmission instances and the corresponding network selection process are modeled by a Markov Decision Process (MDP), for the channel model in the 2-state Markov chain, which can be solved by stochastic dynamic programming. It derives the minimum-cost network selection rule, which can reduce the network cost significantly as compared with the straight-forward scheme with a periodic transmission.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.4 no.2
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• pp.1-8
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• 2005

In this paper, n system did research about effect that interference effect with neighborhood single equipment or group equipment gets in DMB service. For this, 2.6425 GHz SDMB(Satellite Digital Multimedia Broadcasting) that a special of electric wave interference is near frequency-band including interference of signal by unnecessary radiation level that is radiated in UWB system, and degree of 3.4125GHz broadcasting relay net that is In-band frequency-band and interference effect that get in service analyzed comparison ud, modulation of broadcasting relay net and interference measurement equipment used Impulse and OFDM methods. Impulse method was $BER=1{\times}10^4$ that broadcasting signal receiption is possible at 1.4m point because interference effect happens from 2m point in SDMB system, and it was $BER=1^{\times}10-4$ that OFDM method receives interference effect from 0.8m point and broadcasting signal receiption is possible at 0.5m point. Also, about gap-filler center frequency, in case of space interval more than 0.01m, there was no interference effect. Therefore, for the electric wave of W system that is small output applies to system without interference effect in DMB service, confirmed that UWB system of OFDM method is less interference effect than UWB system of impulse method.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.7 no.1
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• pp.23-31
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• 2007

In this paper, UWB system did research about effect that interference effect with neighborhood single equipment or group equipment gets in broadcasting communication service. For this, 2.6425GHz SDMB(Satellite Digital Multimedia Broadcasting) that a special of electric wave interference is near frequency-band including interference of signal by unnecessary radiation level that is radiated in UWB system, and degree of 3.4125GHz broadcasting relay net that is In-band frequency-band and interference effect that get in service analyzed comparison and, modulation of broadcasting relay net and interference measurement equipment used Impulse and OFDM methods. Impulse method was $BER\;=\;1{\times}\;10^{-4}$ that broadcasting signal receiption is possible at 1.4m point because interference effect happens from 2m point in SDMB system, and it was $BER\;=\;1{\times}\;10^{-4}$ that OFDM method receives interference effect from 0.8m point and broadcasting signal receiption is possible at 0.5m point. Also, about Gap-Filler center frequency, In case of space interval more than 0.01m, there was no interference effect. Therefore, for the electric wave of UWB system that is small output applies to system without interference effect in broadcasting communication service, confirmed that UWB system of OFDM method is less interference effect than UWB system of Impulse method.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.04b
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• pp.1161-1164
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• 2001

본 논문에서는 무선 ATM 망에서 VBR(Variable Bit Rate) 트래픽의 QoS(quality of Service)를 보장하고 무선 채널의 효율성을 극대화 할 수 있는 새로운 적응적 슬롯 할당 알고리즘인 In-VDSA를 제안한다. 제안된 알고리즘에서는 ATM 셀 헤더 부분의 GFC(Generic Flow Field) 필드 상에 단말기의 버퍼 상태를 부호화하여 piggybacking하는 방식을 채택하였으며 다음 프레임에 할당할 슬롯의 개수를 기존의 다른 방식과는 달리 유동적으로 조절하여 할당함으로써 단말기의 셀 손실이나 지연에 대한 QoS를 보장하고 채널 이용 효율을 높일 수 있었다. 제안된 알고리즘은 BONeS tool을 이용한 시뮬레이션을 통하여 기존의 방식과 비교 분석한 결과 그 정당성을 확인하였다.

• Journal of Satellite, Information and Communications
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• v.2 no.2
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• pp.59-63
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• 2007

In this paper, we propose an advanced Ka-band satellite HD broadcasting system using scalable video coding technology. As already known, it is not so easy to achieve reasonable link availability on Ka-band because of the rain-attenuation effect, and in case of HD broadcasting service it's more difficult. To overcome that problem, we propose an hierarchical broadcasting system based on H.264 SVC technology. In this paper, we suggest a few types of system scenario to realize the concept. Those scenarios are including DVB-S and DVB-S2 and spatially scalable video stream is the source stream in all cases.

• Journal of Korea Society of Industrial Information Systems
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• v.9 no.2
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• pp.89-95
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• 2004

CDMA is the way that more than one users can share the time and frequency at the same time and connect with multiple access in mobile communication. Multiple Access is indispensible for mobile communication because the limited frequency is able to be used by many users in mobile communication. CDMA is also applied to home network, military, business and medical sectors. This paper, presents a users should share limited frequency resource. CDMA module implemented with 8-layer PCB which consists of the Slice-board circuit, keeping Radio frequency characteristics and a slot type connector.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.245-249
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• 2004

In this paper, we have proposed a clock recovery algorithm of Orthogonal Frequency Division Multiplexing/Quadrature Phase Shift Keying Modulation-Digital Microwave Radio(OFDM/QPSK-DMR) system using Band Limited-Pulse Shaping Filter(BL-PSF) and compared the clock phase error variance of OFDM/QPSK-DMR system with that of single carrier DMR system. The OFDM/QPSK-DMR system using windowing method requires training sequence or Cyclic Prefix (CP) to synchronize the clock phase of received signal. But transmit efficient is increased in our proposed DMR system because of no using redundant data such as training sequence or CP. The proposed clock recovery algorithm is simply realized in the OFDM/QPSK-DMR system using BL-PSF. The simulation results confirm that the proposed clock recovery algorithm has the same clock phase error variance performance in a single carrier DR system under Additive White Gaussian Noise(AWGN) environment.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.2
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• pp.81-88
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• 2018

Spectrum sensing, the key technology of the cognitive radio networks, is used by a secondary user to determine the frequency state of a primary user. The energy detection in the spectrum sensing determines the presence or absence of a primary user according to the intensity of the allocated channel signal. Since this technique simply uses the strength of the signal for spectrum sensing, it is difficult to detect the signal of a primary user in the low SNR band. In this paper, we propose a way to combine spectrum sensing and support vector machine using wavelet packet decomposition to overcome performance degradation in low SNR band. In our proposed scheme, the sensing signals were extracted by wavelet packet decomposition and then used as training data and test data for support vector machine. The simulation results of the proposed scheme are compared with the energy detection using the AUC of the ROC curve and the accuracy according to the SNR band. With simulation results, we demonstrate that the proposed scheme show better determining performance than one of energy detection in the low SNR band.